In computer networks, packets of data are sent from a source to a destination using a number of network elements and links according to various routing protocols. Network elements, such as routers, direct the packets along one or a plurality of links away from the source and towards the destination.
A routing loop may occur during transmission of the packets through the network, such as when an error or failure occurs. As a result, in a group of routers, the path to a particular destination may form a loop, and packets are repeatedly sent back and forth among the group of routers without reaching the intended destination.
In an Internet Protocol (IP) Multicast network where IP Multicast tree building is managed by either Protocol-Independent Multicast (PIM) or multicast Label Distribution Protocol (mLDP), the Unicast control plane plays a fundamental role in ensuring that the information provided to the Multicast control plane is accurate from the perspective of what the current network topology actually is. When the network experiences a link and/or node failure, there is a significant chance that the Multicast control plane, in the effort of trying to restore connectivity for the IP Multicast traffic, will act before the Unicast control plane it is dependent on has been able to converge and reflect the updated topology. The reason for this behavior is that networks supporting IP Multicast services rely on multiple, “ships-in-the-night,” protocols that act independently to build and maintain the necessary state that is associated with the successful delivery of IP Multicast traffic.